The UK has reported a record number of new Covid-19 infections as it battles a surge in cases caused by a variant strain of the disease.
Official figures showed there had been 36,804 new cases and a further 691 deaths within 28 days of a positive test, both up markedly from a day before.
Prime Minister Boris Johnson and his scientific advisers said on Saturday a variant of the coronavirus, which could be up to 70% more transmissible, was spreading rapidly in Britain, although it was not thought to be more deadly or to cause more serious illness.
The authorities have since brought in tight social mixing restrictions measures for London, southeast England and Wales while plans to ease curbs over Christmas across the country have been dramatically scaled back or scrapped altogether.
Many countries, including Ireland, have also closed their borders to the UK due to concern over the mutated strain of the coronavirus.
Home Secretary Priti Patel said ministers had been very proactive over bringing in preventative measures to encourage people to stay at home throughout the Christmas period.
She told BBC radio: "The government has consistently throughout this year been ahead of the curve in terms of proactive measures with regards to coronavirus."
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Meanwhile, Belgium recorded four cases of the mutant strain at the start of December, health officials have said.
The four cases were uncovered at the start of the month in the country's northern Flemish regions that border the Netherlands, said Jan Eyckmans, spokesman for Belgium's health minister.
A spokesman for the national virus crisis centre said the figure was conservative and that other infections by the strain could have gone undetected as Belgium screens for new mutations far less than Britain does.
"It's not much, but it is not impossible that there are more," said Yves Van Laethem.
The infectious diseases expert warned that the decision to close borders could have come too late.
"Isn't the enemy already among us? I don't know, but it's not impossible," he said.
"This closure was perhaps already too late since they started finding cases of this English strain in September."
Elsewhere, Italy has reported 628 coronavirus-related deaths today, compared with 415 yesterday, according to the Italian health ministry.
Italy has also reported 13,318 new Covid-19 cases today, compared with 10,872 yesterday.
The daily tally of new infections increased to 13,318 from 10,872.
After the usual weekend lull, the number of swab tests carried out in the past day rose to 166,205 from a previous 87,889, the ministry said.
The first Western country hit by the virus, Italy has seen 69,842 Covid-19 fatalities since its outbreak emerged in February, the highest toll in Europe and the fifth-highest in the world.
It has also registered some 1.977 million cases to date.
Italian patients in hospital with Covid-19 stood at 24,948 today, down by 197 from the day before. There were 201 new admissions to intensive care units, compared with 161 yesterday.
The actual number of intensive care patients decreased by 44 to 2,687, reflecting those who died or were discharged after recovery.
When Italy's second wave of the epidemic was accelerating fast in the first half of November, hospital admissions were rising by around 1,000 per day, while intensive care occupancy was increasing by about 100 per day.
